The most prominent obstacle to the successful development of renewable energy seems to be the lack of suitable and effective means of energy storage. There are even billboards sponsored by fossil fuel companies along US highways that castigate renewable energy because “the sun doesn't always shine and the wind doesn't always blow.” In the Scientific American March 2012 article “Gather the Wind,” (by Davide Castelvecchi), several wind and solar energy storage concepts are evaluated by a select panel of five experts. The technologies include pumped-hydro, compressed air, heat storage by fluids or molten salts, advanced battery designs, and home hydrogen storage. The technologies are evaluated by experts according to three criteria: 1. how well the technology can be scaled up, 2. the cost-effectiveness of installations, and 3. their efficiency of operation. In brief, none of the technologies fared well from the perspectives of these experts. Even pumped-hydro, the highest scorer in the rankings, faltered over the “lack of suitable sites,” though it fares well as an efficient, cost-effective, and highly reliable method of energy storage (p. 50).
Boone U.S. Pat. No. 7,944,075 discloses energy storage systems using heavy weighted devices. There are essentially three distinct embodiments shown in that patent. They include, first, a large tank or container pulled up a central shaft by a cable. The ultimate power source of the cable is a wind turbine connected by means, such as a motor or direct-geared drive, to run a gearbox and pull the tank up with the cable. (FIG. 16 in that cited patent) Second, a heavy weight can be suspended over a vertical drop and likewise raised on a cable with similar means of motor or direct drive providing power from wind turbines to a gearbox. (FIG. 17) Third, it is possible to use railroad cars filled with a heavy medium that can be pulled up tracks on a steep incline. There will be storage tracks on a horizontal area at the top of the incline to store any number of railroad cars. In all three embodiments, it is then possible, when there is a demand for electricity, to lower the tank, heavy weight, or railroad cars with the cable and use the descending release of weight to drive a generator. (FIGS. 18 and 19)
That suggestion of using a direct mechanical drive by a wind turbine to power a gearbox means that there is no heavy generator in the nacelle and that the intermediate motor to run the gearbox is eliminated. It could lead to reduced costs in wind turbine design and installation and improved efficiencies in the system. All control of electrical generation and speed control to phase properly with the grid would take place at the output side when weight storage is deployed rather than a necessity for turbine operation.